clock() problem

[Ufit]

I must precisely measure the time of calculation.
f.ex

clock_t begin,finish,time;
begin=clock();
Calculations();
finish=clock();
time=finish-begin;

but unfortunatelly finish is equal to begin
sth like begin=56789 and finish=56789
They give me 0. How else can I measure the time very precisely?
Please help.
Thanks

Ufit

[Victor Bazarov]

"Ufit" <ko**************@NOpoczta.fm> wrote...

I must precisely measure the time of calculation.
f.ex

clock_t begin,finish,time;
begin=clock();
Calculations();
finish=clock();
time=finish-begin;

but unfortunatelly finish is equal to begin
sth like begin=56789 and finish=56789
They give me 0. How else can I measure the time very precisely?

You can do more Calculations:

begin=clock();
for (int i=0; i < 1000000; i++)
Calculations();
finish=clock();

or you can use a finer time measurement. Not available in the
Standard C++, but look in your OS programming manual or ask in
the newsgroup dedicated to your OS.

V

[Rickard Nisses-Gagnér]

In Windows you can use GetTickCount() function in Kernel32.dll, just include
windows.h
This function retrievs the number of milliseconds since the computer was
started
And ofcourse use Victors advice!

/Rickard
"Ufit" <ko**************@NOpoczta.fm> skrev i meddelandet
news:cs**********@news.onet.pl...

I must precisely measure the time of calculation.
f.ex

clock_t begin,finish,time;
begin=clock();
Calculations();
finish=clock();
time=finish-begin;

but unfortunatelly finish is equal to begin
sth like begin=56789 and finish=56789
They give me 0. How else can I measure the time very precisely?
Please help.
Thanks

Ufit

[Lionel B]

Rickard Nisses-Gagnér wrote:

/Rickard
"Ufit" <ko**************@NOpoczta.fm> skrev i meddelandet
news:cs**********@news.onet.pl...

I must precisely measure the time of calculation.
f.ex

clock_t begin,finish,time;
begin=clock();
Calculations();
finish=clock();
time=finish-begin;

but unfortunatelly finish is equal to begin
sth like begin=56789 and finish=56789
They give me 0. How else can I measure the time very precisely?
Please help.
Thanks

Ufit

<OT (system-dependent)>
In Windows you can use GetTickCount() function in Kernel32.dll,
just include windows.h
This function retrievs the number of milliseconds since the computer
was started
.... but with a resolution of +/- 10ms (depending on your system) I
believe. On Win NT, QueryPerformanceFrequency() and
QueryPerformanceCounter() (declared in <winbase.h>) are likely to give
you much higher resolution.

</OT>
And ofcourse use Victors advice!

Yes; it will always be unreliable to time just one invocation of a
(fast) function.

--
Lionel B